body {
    /* background: #f2f2f2; */
    background: #282c34;
}

.frame {
    position: absolute;
    top: 50%;
    left: 50%;
    width: 400px;
    height: 400px;
    margin-top: -200px;
    margin-left: -200px;
    border-radius: 2px;
    box-shadow: 1px 2px 10px 0px rgba(0, 0, 0, 0.2);
    overflow: hidden;
    background: #3498db;
    color: #fff;
}

.center {
    position: absolute;
    width: 200px;
    height: 200px;
    top: 100px;
    left: 100px;
    transform-style: preserve-3d;
}

.ring {
    box-sizing: border-box;
    position: absolute;
    top: 0;
    left: 0;
    width: 200px;
    height: 200px;
    border: 1px solid #fff;
    filter: drop-shadow(0px 0px 3px #fff);
    border-radius: 50%;
    transform-origin: 50% 50%;

    animation: rotate 5s ease-in-out infinite;
    animation-delay: calc(var(--i) * 0.1s);
}

@keyframes rotate {
    0% {
        transform: rotateX(0) rotateY(0);
    }
    100% {
        transform: rotateX(360deg) rotateY(-360deg);
    }
}
